OK to leave UMC in the rain?

Looking at the forecast, it appears we may be charging in heavy rain tonight at an RV park.

I'm soliciting any data/opinions on whether it is OK to charge in the rain and to leave the UMC out in the rain all night. I know rain water isn't highly conductive, not like sea water, but I'm more wondering if exposure to rain water might result in corrosion of the 14-50 adapter or mess up our expensive UMC. I'm hoping the plug end of the UMC will be covered by the charge point cover, and the Roadster end looks pretty water tight once attached.

I have a feeling this might be filed along with the time I asked MPT if the magnetic field from the motor would wipe my laptop hard drive. But thanks in advance for any advice.

I'm soliciting any data/opinions on whether it is OK to charge in the rain and to leave the UMC out in the rain all night.

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I was told by Tesla that the UMC was not waterproof... however, upon inspection I think that it's just the connectors used to swap between adaptors. I took the precaution of sealing these connectors using giant heat shrink tubing because I only ever use the 32A 60309 connector with the UMC. I've used the UMC overnight in heavy rain and snow and never had a problem.

I wouldn't worry about it, personally, and I wouldn't be wrapping the electronics in plastic. Just try to keep it a little sheltered and make sure it doesn't sit in a puddle.

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This is an important warning. Sometimes when you wrap stuff in plastic, all you do is create a nice little vessel that holds in water instead of letting it run off. Thus having the opposite of the desired effect.

This is an important warning. Sometimes when you wrap stuff in plastic, all you do is create a nice little vessel that holds in water instead of letting it run off. Thus having the opposite of the desired effect.

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Good point. What I actually did was made little "rain ponchos" for the different parts of the cable, i.e. closed at the top but open at the bottom. That was sort of blind luck. The charging port was sealed with tape at the top but partially open underneath. I posted some pictures over here.

Hopefully water was not the cause of my "line voltage sync" errors. Thanks for the feedback.

P.S. (Edit) The car is charging in the garage now using the same UMC + adapter, which I did not try to dry out. I haven't had any errors yet but will keep an eye on it. I'll also check the connectors for moisture later.

I had my Roadster without a garage from October 2010 through June 2011. During that time, I charged virtually exclusively with the UMC. I left it plugged in (every day) through rain and snow without issue. It was never subject to sitting in a puddle (which I would definitely recommend avoiding). I only unplugged it when I knew I was going to get so much snow that I might not find the cord and/or run over it with the snow blower.
I'd often brush snow out of the receptacle area in the car, and it was often somewhat wet; as long as it wasn't grossly wet in key areas (e.g the actual electrical connections -- which, BTW, I never saw happen), I felt fine plugging it in.

The only times I've run into Line Voltage Sync errors and the like would be problems with the power source (tripped breaker, bad breaker / connection in the panel, voltage drop from insufficient wiring, etc).

I didn't say completely wrap it in plastic. I was meaning make a little bit of a shelter.

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Wasn't implying that you did. Just pointing out something that people often miss.
I had a friend with a broken leg who wrapped her cast in a trash bag so she could take a shower. She ended up with a bag full of water.

Wasn't implying that you did. Just pointing out something that people often miss.
I had a friend with a broken leg who wrapped her cast in a trash bag so she could take a shower. She ended up with a bag full of water.

...I left it plugged in (every day) through rain and snow without issue...

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On the near year anniversary of this thread, I hope people are still following it for something that has come up in question and I had no KNOWLEDGEABLE answer but know that others do. I appreciate you sharing that you never had any incident by charging outdoors in the rain, but my question is from a scientific perspective, is it safe & from a legal perspective, is there anything in the Tesla warranty that invalidates it should you be charging in the rain? My car has always been garaged and, as the song goes, it never rains in Southern California, but there is an occasion where I might be charging it outside in the rain. Please help!

On the near year anniversary of this thread, I hope people are still following it for something that has come up in question and I had no KNOWLEDGEABLE answer but know that others do. I appreciate you sharing that you never had any incident by charging outdoors in the rain, but my question is from a scientific perspective, is it safe & from a legal perspective, is there anything in the Tesla warranty that invalidates it should you be charging in the rain? My car has always been garaged and, as the song goes, it never rains in Southern California, but there is an occasion where I might be charging it outside in the rain. Please help!

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I routinely charge in rain and occasionally snow. It should not be a problem. The HPC is designed for outdoor installation and use. The UMC is also designed for outdoor use even if Tesla doesn't always say that.

Tesla's Roadster connector is sealed on the inside with O-rings and the rubber bushing on the cable end. There is a rubber gasket on the other end that sometimes falls out. It is pushed against the car when you twist-lock it in place, and held tight with a spring. Unfortunately they used a steel spring that is located outside of the waterproof portion. I've seen some that rusted and broke, making it impossible to seal completely. The switch is waterproof (IP-67 rated). The connector that I make uses mostly O-rings to seal it and I also use a much better quality stainless wave spring so it will never rust and break.

There is of course no absolute guarantee that no water will ever seep into any connector. The outer parts that you touch are grounded so in theory it should be safe. If the UMC or HPC is working properly it will not energize the pins until connected to the car.

The HPC is designed for outdoor installation and use. The UMC is also designed for outdoor use even if Tesla doesn't always say that.

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I'm sure of YOUR Can's engineering!
So there is nothing in the Tesla Warranty that voids using the UMC/HPC in the rain? I'm just thinking I don't want to miss some obscure thing like that Mexico controversy!